How to validate if input in input field has base 32 encoded string using express-validator ?
Last Updated :
21 Mar, 2023
In HTML forms, we often required validation of different types. Validate existing email, validate password length, validate confirm password, validate to allow only integer inputs, these are some examples of validation. If In a certain input field, only base 32 encoded strings are allowed i.e. there not allowed any other form of string which does not constitute base32 encoded string. We can also validate these input fields to accept only base 32 encoded strings using express-validator middleware.
Command to install express-validator:
npm install express-validator
Steps to use express-validator to implement the logic:
- Install express-validator middleware.
- Create a validator.js file to code all the validation logic.
- Validate input by validateInputField: check(input field name) and chain on the validation isBase32() with ‘ . ‘
- Use the validation name(validateInputField) in the routes as a middleware as an array of validations.
- Destructure ‘validationResult’ function from express-validator to use it to find any errors.
- If error occurs redirect to the same page passing the error information.
- If error list is empty, give access to the user for the subsequent request.
Note: Here we use local or custom database to implement the logic, the same steps can be followed to implement the logic in a regular database like MongoDB or MySql.
Example: This example illustrates how to validate an input field to accept only base 32 encoded string.
Filename – index.js
javascript
const express = require( 'express' )
const bodyParser = require( 'body-parser' )
const { validationResult } = require( 'express-validator' )
const repo = require( './repository' )
const { validateBase32Data } = require( './validator' )
const formTemplet = require( './form' )
const app = express()
const port = process.env.PORT || 3000
app.use(bodyParser.urlencoded({ extended: true }))
app.get( '/' , (req, res) => {
res.send(formTemplet({}))
})
app.post(
'/data' ,
[validateBase32Data],
async (req, res) => {
const errors = validationResult(req)
if (!errors.isEmpty()) {
return res.send(formTemplet({ errors }))
}
const { name, base32data } = req.body
await repo.create({
name,
base32data
})
res.send( '<h2>Base 32 data decoded and Stored'
+ ' successfully in the database</h2>' )
})
app.listen(port, () => {
console.log(`Server start on port ${port}`)
})
|
Filename – repository.js: This file contains all the logic to create a local database and interact with it.
javascript
const fs = require( 'fs' )
const base32Decode = require( 'base32-decode' )
let ab2str = require( 'arraybuffer-to-string' )
class Repository {
constructor(filename) {
if (!filename) {
throw new Error(
'Filename is required to create a datastore!' )
}
this .filename = filename
try {
fs.accessSync( this .filename)
} catch (err) {
fs.writeFileSync( this .filename, '[]' )
}
}
async getAll() {
return JSON.parse(
await fs.promises.readFile( this .filename, {
encoding: 'utf8'
})
)
}
async create(attrs) {
const records = await this .getAll()
const arrayBuff = base32Decode(
attrs.base32data, 'RFC4648' )
const uint8 = new Uint8Array(arrayBuff)
const data = ab2str(uint8)
const record = {
name: attrs.name,
data
}
records.push(record)
await fs.promises.writeFile(
this .filename,
JSON.stringify(records, null , 2)
)
return record
}
}
module.exports = new Repository( 'datastore.json' )
|
Filename – form.js: This file contains logic to show HTML form.
javascript
const getError = (errors, prop) => {
try {
return errors.mapped()[prop].msg
} catch (error) {
return ''
}
}
module.exports = ({errors}) => {
return `
<!DOCTYPE html>
<html>
<head>
<link rel= 'stylesheet'
<style>
div.columns{
margin-top: 100px;
}
.button{
margin-top : 10px
}
</style>
</head>
<body>
<div class= 'container' >
<div class= 'columns is-centered' >
<div class= 'column is-5' >
<form action= '/data' method= 'POST' >
<div>
<div>
<label class= 'label' id= 'name' >Name</label>
</div>
<input class= 'input' type= 'text' name= 'name'
placeholder= 'Submitted By' for = 'name' >
</div>
<div>
<div>
<label class= 'label' id= 'base32data' >
Base 32 data
</label>
</div>
<input class= 'input' type= 'text'
name= 'base32data'
placeholder= 'Base 32 Encode data'
for = 'citizen' >
<p class= "help is-danger" >
${getError(errors, 'base32data' )}
</p>
</div>
<div>
<button class= 'button is-primary' >
Submit
</button>
</div>
</form>
</div>
</div>
</div>
</body>
</html>
`
}
|
Filename – validator.js: This file contains all the validation logic(Logic to validate an input field to accept only base encoded 32 string).
javascript
const { check } = require( 'express-validator' )
const repo = require( './repository' )
module.exports = {
validateBase32Data: check( 'base32data' )
.trim()
.isBase32()
.withMessage( 'Must be a Base 32 encoded string' )
}
|
Filename – package.json
package.json file
Database:
Database
Online website that converts a normal string to a base 32 string:
Online website that convert a normal string to base 32 string(to show for which string we give base32 input)
Output:
Attempt to submit with invalid base32 string
Response when attempt to submit with invalid base 32 string
Response when attempt to submit with invalid base 32 string
Response when attempt to submit with valid base 32 string
Database after successful submission of form:
Database after successful submission of form
Note: We have used some Bulma classes(CSS framework) in the signup.js file to design the content.
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